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Using Ultrasonic Lamb Waves To Measure Moduli of Composites

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The investigation employs the acousto-ultrasonic configuration with broadband sending and receiving transducers for producing and detecting ultrasonic waves. With the acousto-ultrasonic methods it is possible to observe discrete pulses in the signal. The ultrasonic velocities of these pulses proved sensitive to variations in stiffness modulus and fiber/matrix interfacial shear strength in ceramic matrix composites. There is a need to clarify the nature of Lamb wave modes and to show how they can be used to assess material properties and boundary conditions. It is hoped to thereby demonstrate a method for monitoring mechanical properties of composites. NASA Tech Brief. 8.5" x 11"